You can still study without having a study permit. That’s completely possible and legal provided you act wisely. Courses that have a duration of six months or less can be pursued without a study permit but the visa will not be extended in case of any delay that outlasts the six-month period.
If you are in Canada on a study permit, then your minor children can study without a study permit. This applies to primary and secondary education only. However, foreign nationals are exempted if they pursue short-term course which will be completed before or on the date of their departure from Canada.
For further details, contact Canvas Immigration.